This invention relates to jet drop printing heads of the general type in Beam et al U.S. Pat. No. 3,586,907. Such printing heads comprise an orifice plate for forming a row of liquid jets and a charge ring plate provided with a series of charge rings for selective charging of drops formed by the jets. There are also fluidic elements for supplying printing liquid to the orifice plate, deflection electrode means for deflection of drops charged by the charge rings, and a catcher for catching drops which are so deflected. Non-deflected drops deposit upon a printing medium transported below the print head.
Jet drop print heads of the above described type are inherently capable of high speed, high resolution printing, but there are very exacting manufacturing tolerance requirements. Moreover use of the print head over a long period of time causes erosion of the orifice plate and deposition of contaminants in the fluidic system. Accordingly, it is necessary to disassemble the print head from time to time for refurbishing the fluidic elements and thereafter to reassemble the print head with the charge ring apertures in precise alignment with the jet forming orifices. In the past this has been a very tedious process and one which is difficult for unskilled or semi-skilled operating personnel in a normal operational environment.
The Beam et al print head has a further difficulty in that a plurality of such print heads must be assembled together to provide solid printng coverage. Such an assembly may be accomplished as shown in Cassill U.S. Pat. No. 3,580,515, but there is in any event some difficulty in achieving the necessary alignment accuracy between the different heads. The Beam et al print head was therefore improved by the invention of a new print head arrangement as taught by Mathis U.S. Pat. No. 3,701,998.
The Mathis patent shows a twin row print head capable of solid printing coverage without the cooperation of any other print head. Again there is provision for an orifice plate and a charge ring plate which is in alignment therewith. The Mathis device contemplates an extremely large number of very small diameter jets and at the time of its invention represented a new generation of jet drop print heads. The new level of resolution obtainable by the Mathis device created a requirement for even more accurate alignment between the orifice plate and the charge ring plate.
In order to facilitate assembly and disassembly of jet drop printing elements of the type shown in the Mathis patent there has been developed an improved mounting arrangement as shown in Brady et al U.S. Pat. No. 3,805,273. In this arrangement there is a segregation between the fluidic elements, which are incorporated into an upper assembly, and the electrical elements, which are incorporated into a lower assembly. With such an arrangement it is relatively easy to disassemble the print head for refurbishment of the fluidic package. However, reassembly is a somewhat tedious process because of the above mentioned requirement for precision alignment between the orifice plate, now part of the upper assembly and the charge ring plate, which is part of the lower assembly. Also, for improved operation in the field, it has become desirable to improve the catcher mounting arrangement and extend operating life of the fluidic package.